Many server placement proposals [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]} have assumed that each base station can be only associated with one edge cloud in their formulations. With this assumption, many standard algorithms, e.g., k-means clustering algorithm, set cover algorithm, etc., can be used to design heuristic solutions for the server placement problem. However, this formulation is inherently non-robust to demand uncertainty. Whenever the workload of a base station bursts, the edge cloud that serves this base station has to bear the burden by itself. In fact, for a given server placement, EC users do benefit from offloading their job requests to multiple edge clouds[10]}, [11]}. There does exist literature [12]}, [13]}, [14]}, [15]} that allows serving workload from the same base station in different edge clouds. However, workload uncertainty is not considered therein.
